1. Field of the Invention
This invention relates generally to therapeutic beds, and more particularly to an improved rotating bed capable of placing a patient in a prone position.
2. Long-felt Needs and Description of the Related Art
Patient positioning has been used in hospital beds for some time to enhance patient comfort, prevent skin breakdown, improve drainage of bodily fluids, and facilitate breathing. One of the goals of patient positioning has been maximization of ventilation to improve systematic oxygenation. Various studies have demonstrated the beneficial effects of body positioning and mobilization on impaired oxygen transport. The support of patients in a prone position can be advantageous in enhancing extension and ventilation of the dorsal aspect of the lungs.
Proning has been recognized and studied as a method for treating acute respiratory distress syndrome (“ARDS”) for more than twenty-five years. Some studies indicate that approximately three quarters of patients with ARDS will respond with improved arterial oxygenation when moved from the supine to the prone position.
There are several physiological bases for patient proning. When a person lies flat in the supine position, the heart and sternum lie on top of and compress the lung volume beneath it. Moreover, the abdominal contents push upward against the diaphragm and further compress and increase the pressures on the most dorsal lung units, where perfusion (i.e., blood flow volume reaching alveolocapillary membranes) is greatest. In an ARDS patient, ventilation in these dorsal regions is inhibited by fluid and cellular debris that settle into the most dependent lung segments. Lung edema may further increase the plural pressures in the most dependent regions. The combination of fluid accumulation with compression by the heart, sternum, and abdominal contents on the dorsal regions of the lung results in a significant ventilation-perfusion mismatch. Expressed more simply, the air entering the patient's lungs is not reaching those parts of the lungs (the dorsal regions where perfusion is greatest) that most need it.
Flipping a patient into the prone position improves arterial oxygenation through several mechanisms. First, moving the fluid-filled lungs into a nondependent ventral position facilitates drainage of the fluid and cellular debris that had accumulated in and blocked ventilation to the dorsal regions of the lung. Second, the weight of the heart is supported by the sternum, rather than the lungs. When a patient is in the supine position, as much as 25-44% of the lung volume may be displaced by the heart, especially if the heart is enlarged due to cardiovascular disease. Rotating the patient into the prone position can reduce that displacement to as little as 1-4% of lung volume. Third, if the patient is supported in the prone position in a manner that allows the abdomen to protrude, then the abdominal contents no longer push upward onto the diaphragm to compress the lungs.
Proning minimizes the mechanical forces that pressurize distressed alveolar units into collapse, and can also recruit atelectatic but functional units for gas exchange. Proning also causes changes in pleural pressures, which encourages more uniform distribution of ventilation within the lungs. Proning often reduces the intrapulmonary shunt (defined as the portion of blood that enters the left side of the heart without exchanging gases with alveolar gases) and improves arterial oxygenation. The results of proning can be immediate, resulting in significantly improved oxygenation in as little as one hour.
Despite its promises, prone positioning has not been widely practiced on patients because, due to the inadequacies of prior art devices, it is a difficult and labor-intensive process. Logistically, moving a patient to the prone position using prior art technology requires careful planning, coordination, and teamwork to prevent complications such as inadvertent extubation and loss of invasive lines and tubes.
Even when precautions are taken, proning using prior art technology is fraught with potential complications. For example, it is difficult to provide cardiopulmonary resuscitation (“CPR”) to a patient lying in the prone position. Critical time may have to be spent recruiting a team of personnel to move the patient from the prone to the supine position before performing CPR. Accordingly, there is a need for a motor-operated proning device that will quickly rotate a proned patient from the prone position to the supine position. There is also a need for a system that enables a fast, one-step operation to cause the motor-operated proning device to rotate the patient back to a supine position.
A frequently cited complication with prone positioning is the development of pressure ulcers, especially on the forehead, chin, and upper chest wall. Immobility in the prone position can also result in breast and penile breakdown. Some of the most difficult areas to manage in the prone position are the head, face, eyes, and arms. Increased incidence of eye infection due to drainage, corneal abrasions, and even blindness caused by increased intraocular pressure have been reported as a consequence of prone positioning. Also, immobility and pressure on the arms have been reported to result in peripheral nerve injury and contractures. Accordingly, there is a need for a proning device that minimizes the risk of pressure-related complications.
Proning can also increase the risk of aspiration of gastric acid, food, or other foreign material into the lungs. Aspiration of gastric acid can result in severe pneumonia. Another complication, much more frequent than aspiration, is dependent edema. Most critically ill intensive care unit patients develop dependent edema. When moved into the prone position, the face is put into a dependent position, which often results in significant facial edema. Accordingly, there is a need for a proning device that will minimize aspiration and facial edema.
There are many prior art devices used to facilitate patient proning. One example is the Vollman Prone Device™, made by the Hill-Rom Co., Inc.™ The Vollman Prone Device comprises a set of foam pads to support the patient's head, chest, and pelvis and which are secured to a patient with straps, belts, and buckles while the patient in the supine position. After the foam pads are secured, the patient is manually rotated into the prone position on a regular hospital mattress. Of course, no special device is needed to place a patient in the prone position. Towels, blankets, egg crate mattresses, and foam positioning pads can be used to help maintain proper alignment in the prone position.
One difficulty with devices such as the Vollman Prone Device is that several personnel are still required to turn the patient over. Moreover, medical personnel must revisit the patient frequently to turn the patient toward different positions to prevent pressure sores and other complications from developing.
To make it easier to turn a patient into the prone position, other prior art devices have been provided comprising a rotatable frame to rotate a patient into the prone position. The Stryker Wedge™ Turning Frame, for example, comprises a rotatable frame having a supine support surface and a prone support surface in between which a patient is wedged. The frame is manually rotated into the desired position. But the frame still suffers several shortcomings. One of its shortcomings, as with other manually-operated prior art proning devices, is inadequate compliance by medical personnel. Because it is difficult and labor intensive to manually operate a proning bed, many doctors do not begin proning ARDS patients until late in the course of the patient's disease process, after other recruitment measures have failed. However, there is a general consensus that if prone positioning is provided earlier, in the more exudative stages of ARDS, a patient will be more likely to respond positively. Accordingly, there is a need for a therapeutic bed that makes it simpler and less labor-intensive for medical personnel to prone a patient.
Another problem with manually-operated prior art beds such as the Stryker Wedge Frame is that unless manually rocked back and forth, patients will be left immobile, in a fixed position, for extended periods of time. Immobility leads to many of the complications discussed above that hinder the widespread adoption of prone positioning as a therapy for ARDS patients. Accordingly, there is a need for a therapeutic bed that provides not only prone positioning but also automated alternating side-to-side rotational therapy to intermittently relieve pressure from the dependent surfaces of the body.
Other beds made by Kinetic Concepts, Inc.®, such as the TriaDyne® II, also facilitate prone positioning. Specially designed proning cushions have been provided to accommodate moving a patient to the prone position and maintaining the patient there. The TriaDyne's low air loss pressure relief surface reduces the risk of certain complications like skin breakdown. While the TriaDyne has many benefits, its protocol calls for a team of about 5 to 8 people to move a patient from the supine to the prone position. One person should be assigned at the head of the bed to secure and manage the airway during the maneuver. The procedure also calls for the team to disconnect as many of the invasive lines as possible to simply the procedure, and then reconnect them when the patient has been placed in the prone position. Caution must be exercised with head positioning to prevent applying pressure directly to the eyes, ears, or endotracheal tube.
While it is possible to program the TriaDyne to perform continuous lateral rotation therapy while the patient is in the prone position, the TriaDyne is incapable of automatically rotating the patient from the supine to the prone position, and from there applying kinetic therapy. Moreover, the arc of rotation in the prone position is limited because of the absence of restraints to keep the patient centered on the bed while turning to a significant angle from the prone position. In practice, the range of motion in the TriaDyne is generally limited to no more than 30 degrees to the left and right of prone. The Centers for Disease Control (“CDC”) defines kinetic therapy as lateral rotation of greater than 40 degrees to the horizontal left and right, or an arc of at least 80 degrees.
Moreover, the TriaDyne and many other beds are not capable of rotation beyond 62 degrees from even the supine position, much less so from the prone position, because the beds lack restraints to hold the patient on the bed. It is the belief of the inventors that further therapeutic benefits could be obtained by rotating patients to angle limits beyond 62 degrees in either direction, to, for example, 90 degrees or more in either direction, in order to recruit further areas of a collapsed lung to participate in gas exchange, and also to further reduce pressure on the dorsal regions of the patient's body. Accordingly, there is a need for a therapeutic bed that can automatically rotate a patient from the supine to the prone position and back, and that is capable of providing kinetic therapy (i.e., with an arc of at least 80 degrees) while still securing the patient to the center of the bed.
Another type of prone positioning bed comprises a base frame, a patient support platform rotatably mounted on the base frame for rotational movement about a longitudinal rotational axis of the patient support platform, and a drive system for rotating the patient support platform on the base frame. Such therapeutic beds are described in international patent applications having publication numbers WO 97/22323 and WO 99/62454. This type of bed is particularly advantageous for the treatment of patients with severe respiratory problems.
One of the problems in the art of prone positioning therapeutic beds is to sufficiently support the head of a patient during rotation. In the past, elastic straps have been stretched across the patient's head to secure the head to the patient support platform. However, such straps are generally uncomfortable for the patient and do not provide sufficient lateral support for the patient's head. Additionally, such straps do not provide sufficient adjustability. It would be a significant improvement to provide a comfortable, adjustable head restraint that supports the patient's head both laterally and vertically.
Typically, prone positioning beds have lateral support pads for supporting the sides or legs of the patient during rotation. It is known in the art for such lateral support pads to be laterally adjustable. For purposes of rotational stability, it is desirable for the patient to be centered on the patient support platform. Therefore, it would be an advancement in the art to provide adjustable lateral support pads that automatically center the patient on the patient support platform. In conjunction with automatically centering lateral support pads, it would also be an advancement to provide symmetric leg abductors.